"... Many large decentralized systems rely on information propagation to ensure their proper function. We examine a common scenario in which only participants that are aware of the information can compete for some reward, and thus informed participants have an incentive not to propagate information to ot ..."

to others. One recent example in which such tension arises is the 2009 DARPA Network Challenge (finding redballoons). We focus on another prominent example: Bitcoin, a decentralized electronic currency system. Bitcoin represents a radical new approach to monetary systems. It has been getting a large amount

"... In this letter we present a brief report of our recent research on information distribution mechanisms in networks [Babaioff et al. 2011]. We study scenarios in which all nodes that become aware of the information compete for the same prize, and thus have an incentive not to propagate information. E ..."

. Examples of such scenarios include the 2009 DARPA Network Challenge (finding redballoons), and raffles. We give special attention to one application domain, namely Bitcoin, a decentralized electronic currency system. We propose reward schemes that will remedy an incentives problem in Bitcoin in a Sybil

"... Online social networks offer unprecedented potential for rallying a large number of people to accomplish a given task. Here we focus on information gathering tasks where rare information is sought through ‘‘referral-based crowdsourcing’’: the information request is propagated recursively through inv ..."

RedBalloon Challenge where the level of misreporting was very high. In order to undertake a formal study of verification, we introduce a model where agents can exert costly effort to perform verification and false reports can be penalized. This is the first model of verification and it provides many

"... Online social networks offer unprecedented potential for rallying a large number of people to accomplish a given task. Here we focus on information gathering tasks where rare information is sought through ‘‘referral-based crowdsourcing’’: the information request is propagated recursively through inv ..."

RedBalloon Challenge where the level of misreporting was very high. In order to undertake a formal study of verification, we introduce a model where agents can exert costly effort to perform verification and false reports can be penalized. This is the first model of verification and it provides many

"... Abstract. An exciting application of crowdsourcing is to use social networks in complex task execution. In this paper, we address the problem of a planner who needs to incentivize agents within a network in order to seek their help in executing an atomic task as well as in recruiting other agents to ..."

Abstract. An exciting application of crowdsourcing is to use social networks in complex task execution. In this paper, we address the problem of a planner who needs to incentivize agents within a network in order to seek their help in executing an atomic task as well as in recruiting other agents to execute the task. We study this mechanism design problem under two natural resource optimization settings: (1) cost critical tasks, where the planner’s goal is to minimize the total cost, and (2) time critical tasks, where the goal is to minimize the total time elapsed before the task is executed. We identify a set of desirable properties that should ideally be satisfied by a crowdsourcing mechanism. In particular, sybilproofness and collapse-proofness are two complementary properties in our desiderata. We prove that no mechanism can satisfy all the desirable properties simultaneously. This leads us naturally to explore approximate versions of the critical properties. We focus our attention on approximate sybil-proofness and our exploration leads to a parametrized family of payment mechanisms which satisfy collapse-proofness. We characterize the approximate versions of the desirable properties in cost critical and time critical domain. 1

"... We study Incentive Trees for motivating the participation of people in crowdsourcing or human tasking systems. In an Incentive Tree, each participant is rewarded for contributing to the system, as well as for soliciting new participants into the system, who then themselves contribute to it and/or th ..."

We study Incentive Trees for motivating the participation of people in crowdsourcing or human tasking systems. In an Incentive Tree, each participant is rewarded for contributing to the system, as well as for soliciting new participants into the system, who then themselves contribute to it and/or themselves solicit new participants. An Incentive Tree mechanism is an algorithm that determines how much reward each individual participant receives based on all the participants’ contributions, as well as the structure of the solicitation tree. The sum of rewards paid by the mechanism to all participants is linear in the sum of their total contribution. In this paper, we investigate the possibilities and limitations of Incentive Trees via an axiomatic approach by defining a set of desirable properties that an incentive tree mechanism should satisfy. We give a mutual incompatibility result showing that there is no incentive tree mechanism that simultaneously achieves all the properties. We then present two novel families of incentive tree mechanisms. The first family of mechanisms achieves all desirable properties, except that it fails to protect against a certain strong form of multi-identity attack; the second set of mechanisms achieves all properties, including the strong multi-identity protection, but fails to give participants the opportunity to achieve unbounded reward. Given the above impossibility result, these two mechanisms are effectively the best we can hope for. Finally, our model and results generalize recent studies on multi-level marketing mechanisms.

"... In this paper, we study incentive mechanisms for retrieving information from networked agents. Following the model in [Kleinberg and Raghavan 2005], the agents are represented as nodes in an infinite tree, which is generated by a random branching process. A query is issued by the root, and each node ..."

In this paper, we study incentive mechanisms for retrieving information from networked agents. Following the model in [Kleinberg and Raghavan 2005], the agents are represented as nodes in an infinite tree, which is generated by a random branching process. A query is issued by the root, and each node possesses an answer with an independent probability p = 1/n. Further, each node in the tree acts strategically to maximize its own payoff. In order to encourage the agents to participate in the information acquisition process, an incentive mechanism is needed to reward agents who provide the information as well as agents who help to facilitate such acquisition. We focus on designing efficient sybil-proof incentive mechanisms, i.e., which are robust to fake identity attacks. We propose a family of mechanisms, called the direct referral (DR) mechanisms, which allocate most reward to the information holder as well as its direct parent (or direct referral). We show that, when designed properly, the direct referral mechanism is sybil-proof and efficient. In particular, we show that we may achieve an expected cost of O(h 2) for propagating the query down h levels for any branching factor b> 1. This result exponentially improves on previous work when requiring to find an answer with high probability. When the underlying network is a deterministic chain, our mechanism is optimal under some mild assumptions. In addition, due to its simple reward structure, the DR mechanism might have good chance to be adopted in practice.